JP2013160128A - Reducing agent adding system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reducing agent adding system for injecting an ammonia-based reducing agent from an adding valve on the turbine downstream side of a turbocharger, configured to uniformly disperse the ammonia-based reducing agent without increasing back pressure of an internal combustion engine, and to enable quick hydrolysis for urea water.SOLUTION: High-temperature high-pressure exhaust gas on the upstream side of a turbine 4b is jetted from an exhaust gas jetting mechanism 26 to a space area SU where droplets of urea water injected from a urea water adding valve 14 exist. The urea water is sufficiently and uniformly dispersed over the whole exhaust gas flow, generates ammonia by facilitating hydrolysis of urea, and reaches an SCR catalyst 20 on the downstream side. The ammonia can be sufficiently and uniformly supplied to the whole SCR catalyst 20 without sticking the urea to an inner wall of an exhaust pipe 12. The exhaust gas jetting mechanism 26 jets exhaust gas to the space area Su by bypassing the exhaust gas on the upstream side of the turbine 4b to the downstream side, thereby preventing increase in back pressure of a diesel engine 2.

Description

  The present invention relates to an ammonia-based reducing agent in a catalyst disposed downstream of an exhaust pipe by injecting the ammonia-based reducing agent into exhaust gas in the exhaust pipe from an addition valve disposed downstream of the turbocharger turbine in the exhaust pipe of the internal combustion engine. It is related with the reducing agent addition system which supplies.

  An SCR (Selective Catalytic Reduction) system is known as a nitrogen oxide purification device that reduces NOx (nitrogen oxide) discharged from an internal combustion engine. In this SCR system, for example, by injecting an ammonia-based reducing agent such as urea aqueous solution (so-called urea water) or ammonia gas into the exhaust pipe, the nitrogen oxide purifying catalyst existing downstream, by the reducing action of ammonia, NOx contained in the exhaust is selectively reduced to nitrogen or water. When urea water is injected into the exhaust pipe, ammonia is generated by hydrolysis of urea in the high-temperature exhaust gas.

  When such an ammonia-based reducing agent is injected into the exhaust pipe, if its concentration is biased in the exhaust gas, the downstream catalyst may be biased in the reducing action depending on the location, which may reduce the purification efficiency. . Therefore, in order to supply the ammonia-based reducing agent uniformly to the entire downstream catalyst, it is necessary to quickly and uniformly disperse the ammonia-based reducing agent in the entire exhaust stream immediately after injection.

  Further, in the case where hydrolysis is required as in the case of urea water, uniform dispersion is required as described above, and further, the necessity of heating the injected urea water quickly and sufficiently for hydrolysis, and urea There is a need to prevent crystals from adhering to the inner wall of the exhaust pipe in a solidified state.

  As a countermeasure to such a problem, by arranging a guide in which two guide pipes are combined in the exhaust pipe, the exhaust flow direction is changed to cause the exhaust to collide with each other, or the exhaust flow is speeded up. A technique is known in which urea water is uniformly dispersed in exhaust gas and urea crystals are not attached to the inner wall of the exhaust pipe (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2011-038458 (pages 8-9, FIG. 2)

  However, in the technique of Patent Document 1, since a guide pipe that becomes a flow resistance is arranged in the exhaust flow in order to increase the collision and flow velocity of the exhaust flow, the back pressure increases and the fuel consumption of the internal combustion engine deteriorates.

  Furthermore, in the technique of Patent Document 1, an addition valve for injecting urea water is arranged for an internal combustion engine equipped with a turbocharger. In this case, the addition valve is provided on the downstream side of the turbine of the turbocharger in order to prevent the precipitation of urea from affecting the turbine and to prevent adhesion of the urea water addition valve to a high temperature.

  However, after passing through the turbine, the exhaust flows without being sufficiently agitated. For this reason, depending on the operating state of the internal combustion engine, there is a risk that the uniform dispersion in the entire exhaust flow may become insufficient before reaching the catalyst. This may result in insufficient purification efficiency in the catalyst.

  Furthermore, urea water is injected downstream from the upstream side of the turbine where the exhaust temperature is lower, so ammonia generation due to urea hydrolysis is insufficient before reaching the catalyst, which enables uniform dispersion and rapid purification. May become difficult.

  The present invention provides a reductant addition system that injects an ammonia reductant from an addition valve downstream of a turbine of a turbocharger, and uniformly distributes the ammonia reductant in the entire exhaust flow without increasing the back pressure of the internal combustion engine. It is an object of the present invention to provide a reducing agent addition system that can be improved and can be rapidly hydrolyzed when the ammonia-based reducing agent is urea water.

In the following, means for achieving the above-mentioned purpose, and its operation and effect are described.
The reducing agent addition system according to claim 1 is arranged downstream of the exhaust pipe by injecting ammonia-based reducing agent into the exhaust gas in the exhaust pipe from an addition valve arranged downstream of the turbocharger turbine in the exhaust pipe of the internal combustion engine. A reducing agent addition system for supplying an ammonia-based reducing agent to the prepared catalyst, comprising an exhaust ejection mechanism for ejecting exhaust gas upstream of the turbine in a space region in the exhaust pipe in the injection direction of the addition valve. It is characterized by.

  During operation of the internal combustion engine, the exhaust on the upstream side of the turbine of the turbocharger is at a higher temperature and pressure than the exhaust on the downstream side. The exhaust jet mechanism ejects the high-temperature and high-pressure exhaust into a space region in the exhaust pipe in the injection direction with respect to the addition valve that injects the ammonia-based reducing agent on the downstream side of the turbine.

  The exhaust gas thus ejected is at a higher temperature and pressure than the surrounding exhaust gas containing the ammonia-based reducing agent. For this reason, in the space area where the ammonia-based reducing agent is injected from the addition valve, a vigorous jet is generated by the high-temperature and high-pressure exhaust, and the space area containing the ammonia-based reducing agent is vigorously stirred at a high temperature.

  For this reason, as compared with conventional cases where ammonia-based reducing agent is simply injected into the exhaust from the addition valve, or when a guide pipe is arranged in the exhaust flow downstream of the turbine to increase the direction and speed of the exhaust flow. Thus, the ammonia-based reducing agent is sufficiently evenly dispersed throughout the exhaust stream before more intense agitation occurs and reaches the downstream catalyst.

As a result, the ammonia-based reducing agent is uniformly supplied to the entire catalyst.
Further, when the ammonia-based reducing agent is urea water, the droplets are quickly and uniformly dispersed in the exhaust gas as described above, and the exhaust gas that performs the dispersion is hot, so Rapidly changes to ammonia with accelerated decomposition. For this reason, urea does not precipitate and adhere to the inner wall of the exhaust pipe, and ammonia can be supplied uniformly to the entire catalyst.

  Such a rapid uniform dispersion of the ammonia-based reducing agent into the exhaust gas, and further, a rapid hydrolysis of urea in the case of urea water, is caused by the exhaust jet mechanism in the space region in the exhaust pipe downstream from the turbine. This is done by ejecting the exhaust on the upstream side. For this reason, the back pressure of the internal combustion engine does not increase.

The reducing agent addition system according to claim 2 is characterized in that, in the reducing agent addition system according to claim 1, the ammonia-based reducing agent is urea water.
Thus, when urea water is used as an ammonia-based reducing agent, introduction of high-temperature and high-pressure exhaust becomes more effective. That is, as described above, the urea water droplets are rapidly and uniformly dispersed in the exhaust gas, and urea is rapidly hydrolyzed into ammonia because the process is under high temperature. Therefore, even if urea water is used as the ammonia reducing agent, urea does not precipitate and adhere to the inner wall of the exhaust pipe.

  In the reducing agent addition system according to claim 3, in the reducing agent addition system according to claim 1 or 2, the exhaust jet mechanism is provided in a bypass pipe that bypasses from the upstream side of the turbine to the downstream side, and the bypass pipe is provided. And a control unit for controlling the valve.

  The exhaust injection mechanism includes the bypass pipe, the valve, and the control unit described above, and the control unit controls the valve as necessary, so that the exhaust on the upstream side of the turbine can be discharged from the addition valve via the bypass pipe. It can be ejected to the space area in the exhaust pipe in the ejection direction. Therefore, exhaust energy can be used efficiently.

  The reducing agent addition system according to claim 4, wherein in the reducing agent addition system according to claim 3, the control unit controls the valve in accordance with an addition period of the ammonia-based reducing agent from the addition valve. Then, the exhaust gas upstream of the turbine is ejected.

  The addition period of the ammonia reducing agent varies depending on the state of the catalyst. For this reason, by determining the timing of exhaust emission on the upstream side of the turbine corresponding to the addition period of the ammonia-based reducing agent, exhaust gas is efficiently discharged without unnecessarily causing high-temperature and high-pressure exhaust to be injected downstream of the turbine. Can be used.

  In the reducing agent addition system according to claim 5, in the reducing agent addition system according to claim 4, the control unit has an exhaust temperature in a region where urea water is added as an ammonia reducing agent by the addition valve. When the temperature is lower than a reference temperature, the valve is controlled to discharge exhaust gas upstream of the turbine.

  When urea water is added as an ammonia-based reducing agent, high-temperature and high-pressure exhaust is not ejected downstream from the turbine upstream in an internal combustion engine operating state where exhaust temperature is low downstream of the turbine and rapid urea hydrolysis is difficult. Then, urea may accumulate on the inner wall of the exhaust pipe, or the reduction action with the catalyst may not be sufficiently performed.

  Conversely, in an operating state where the exhaust gas temperature downstream of the turbine is sufficiently high, even if high-temperature and high-pressure exhaust gas is not ejected downstream from the upstream side of the turbine, due to intense expansion due to water vaporization of urea water and rapid hydrolysis reaction of urea, Rapid production of ammonia and its uniform dispersion are realized.

  For this reason, only when the exhaust temperature in the region where the urea water is added is lower than the reference temperature, the control unit controls the valve to eject the exhaust upstream of the turbine. As a result, unnecessarily high temperature exhaust gas is not ejected downstream of the turbine, so that the use of exhaust energy becomes more efficient.

1 is a configuration diagram of a reducing agent addition system according to Embodiment 1. FIG. (A), (B) Structure explanatory drawing of the vertical cross section and bottom face of the ejection part of the exhaust ejection mechanism in the reducing agent addition system of Embodiment 1. FIG. The block diagram of the reducing agent addition system of Embodiment 2. FIG. 7 is a flowchart of exhaust ejection control processing executed by the ECU according to the second embodiment. 10 is a flowchart of an exhaust ejection control process executed by an ECU according to the third embodiment. FIG. 6 is a configuration explanatory diagram of a urea water addition valve and a jet part in the reducing agent addition system of the fourth embodiment. (A), (B) Structure explanatory drawing of the ejection part of Embodiment 4. FIG.

[Embodiment 1]
<Configuration of Embodiment 1> FIG. 1 shows a configuration of a reducing agent addition system to which the above-described invention is applied. The reducing agent addition system is applied to an exhaust system of an internal combustion engine, here, a diesel engine 2. The diesel engine 2 is provided with a turbocharger 4. The intake air on the intake pipe 6 side is supercharged by the compressor 4 a, cooled by the intercooler 8, and supplied to each cylinder of the diesel engine 2.

  The exhaust of the diesel engine 2 gives rotational energy to the turbine 4b for the supercharging. Thereafter, the exhaust is discharged to the exhaust pipe 12 on the downstream side of the turbine 4b at a lower temperature and lower pressure than the upstream side of the turbine 4b.

  A urea water addition valve 14 is disposed in the exhaust pipe 12 on the downstream side of the turbine 4b, and urea water (urea aqueous solution) is injected into the exhaust pipe 12. Urea water is supplied from a urea water storage tank 18 to the urea water addition valve 14 via a pump 16.

  The urea water droplets injected into the exhaust gas from the urea water addition valve 14 are dispersed in the exhaust gas flowing in the exhaust pipe 12, and the urea is hydrolyzed by the heat of the exhaust gas. This generates ammonia. This ammonia performs NOx purification at the downstream SCR catalyst 20 as an ammonia-based reducing agent.

  The urea water addition valve 14 and the pump 16 are driven by an electronic control circuit. Here, the drive is controlled according to the operation state of the diesel engine 2, and NOx discharged from the diesel engine 2 is appropriately purified by ammonia generated by hydrolysis of urea water in the SCR catalyst 20.

  In the exhaust system, a bypass path 22 is provided to bypass the exhaust from the upstream side to the downstream side of the turbine 4b. This bypass path 22 is a pipe line that introduces the high-temperature and high-pressure exhaust upstream of the turbine 4b to the downstream side of the turbine 4b, which has a low temperature and low pressure. An ejection portion 24 is formed at a connection portion between the bypass passage 22 and the exhaust pipe 12 on the downstream side of the turbine 4b.

  As shown in FIG. 2A, the ejection portion 24 has a box shape and is fixed through the exhaust pipe 12 so as to form a part of the wall surface of the exhaust pipe 12. The ejection portion 24 opens to the accumulation chamber 24a for temporarily accumulating high-temperature and high-pressure exhaust from the bypass passage 22 and the inner wall portion 24b inside the exhaust pipe 12 as shown in FIG. Three jet outlets 24c for jetting high-temperature and high-pressure exhaust gas into low-temperature and low-pressure exhaust gas are provided.

  The inner wall portion 24 b of the ejection portion 24 is curved corresponding to the inner surface of the exhaust pipe 12, and the three outlets 24 c are spaces in the exhaust pipe 12 in the urea water injection direction of the urea water addition valve 14. It is directed to the area Su.

That is, by forming the exhaust ejection mechanism 26 by the bypass path 22 and the ejection part 24, the exhaust ejection mechanism 26 can eject exhaust gas upstream of the turbine 4b into the space region Su.
<Operation of First Embodiment> High-temperature and high-pressure exhaust is ejected from the exhaust ejection mechanism 26 to the space region Su where the droplets of urea water sprayed from the urea water addition valve 14 are present. The exhaust gas thus ejected is at a higher temperature and pressure than the surrounding exhaust gas containing urea water. For this reason, in the space region Su, a violent jet is generated by high-temperature and high-pressure exhaust, including violent expansion due to moisture vaporization, and the space region Su is vigorously stirred in a high temperature state.

Therefore, when urea water is simply injected into the exhaust gas from the urea water addition valve 14 as in the conventional case, or as shown in the background art, a guide pipe is arranged in the exhaust flow downstream of the turbine 4b, and the direction of the exhaust flow and the high speed Compared with the case of achieving the above, in the configuration of the present embodiment, more intense stirring occurs at a higher temperature.
<Effect of Embodiment 1> (1) Therefore, before reaching the SCR catalyst 20 on the downstream side, the urea water is sufficiently uniformly dispersed in the entire exhaust gas stream, and the hydrolysis of urea is promoted to make the whole Change to ammonia. Thus, ammonia can be supplied sufficiently uniformly to the entire SCR catalyst 20 without urea adhering to the inner wall of the exhaust pipe 12.

  Such a rapid uniform dispersion of urea water in the exhaust and rapid hydrolysis of urea water are performed by the exhaust ejection mechanism 26 in the space region Su in the exhaust pipe 12 in the injection direction of the urea water addition valve 14. Since it is executed by jetting exhaust gas upstream of the turbine 4b, the back pressure of the diesel engine 2 does not increase.

  (2) Since the exhaust ejection mechanism 26 promotes the dispersion of urea water, the required performance on the mechanism for urea water addition such as the spray particle diameter by the urea water addition valve 14 and the capacity of the pump 16 is eased. For this reason, an inexpensive thing can be employ | adopted as a urea water addition mechanism.

[Embodiment 2]
<Configuration of Embodiment 2> In this embodiment, the configuration is as shown in FIG. Here, the ECU (electronic control unit) 130 as the control unit, like the first embodiment, based on the operation state of the diesel engine and other information, the urea water addition valve 114 and the urea water storage tank 118. And the pump 116 that pumps the urea water to the urea water addition valve 114 is executed. Further, in the present embodiment, the exhaust ejection mechanism 126 that introduces the exhaust on the upstream side of the turbine into the exhaust pipe 112 on the downstream side includes the bypass passage 122 and the ejection portion 124 as in the first embodiment. However, it further includes a valve 122a for opening and closing the bypass passage 122 and an actuator 122b for driving the valve 122a.

The actuator 122b is controlled by the ECU 130. Accordingly, high-temperature and high-pressure exhaust is ejected into the space region Su in the exhaust pipe 112 via the bypass passage 122 and the ejection portion 124 at the timing based on the exhaust ejection control process shown in the flowchart of FIG. 4. Other configurations are the same as those of the first embodiment.
<Operation of Second Embodiment> The operation of the present embodiment will be described based on the processing shown in FIG. The process of FIG. 4 is a process that is repeatedly executed every short period, for example, every 10 ms. Steps in the flowchart corresponding to individual processing contents are represented by “S˜”.

  When this process is started, it is first determined whether or not there is a urea water injection request in the urea water injection process separately executed by the ECU 130 (S100). If there is no urea water injection request (NO in S100), a closing instruction for the valve 122a provided in the bypass path 122 is output to the actuator 122b (S104). As a result, the actuator 122b closes the valve 122a if the valve 122a is in an open state just before, and maintains the state if the valve 122a is already in a closed state. Therefore, the high-temperature and high-pressure exhaust upstream of the turbine is not ejected from the ejection part 124 into the exhaust pipe 112 on the downstream side.

On the other hand, if there is a urea water injection request (YES in S100), that is, if it is an addition period in which urea water is sprayed from the urea water addition valve 114 into the exhaust gas by this request, an opening command for the valve 122a is issued. The data is output to the actuator 122b (S102). Thus, in the actuator 122b, the valve 122a is opened if the valve 122a is closed by just before, and the state is maintained if the valve 122a is already open. Therefore, high-temperature and high-pressure exhaust upstream of the turbine is ejected from the ejection portion 124 into the exhaust pipe 112 on the downstream side. As a result, high-temperature and high-pressure exhaust gas flows at high speed into the space region Su in the downstream exhaust pipe 112 where urea water droplets injected from the urea water addition valve 114 are present, and sprayed urea. Stir while heating water. As a result, urea is rapidly hydrolyzed, and the produced ammonia is uniformly dispersed, so that ammonia can be supplied sufficiently uniformly to the entire downstream SCR catalyst 120.
<Effects of Second Embodiment> (1) The effects of the first embodiment are produced. At the same time, the bypass 122 is provided with a valve 122a, and if necessary, that is, during the urea water addition period, the high-temperature and high-pressure exhaust gas upstream of the turbine is ejected. doing. For this reason, exhaust gas of high temperature and high pressure is not unnecessarily ejected downstream of the turbine, and exhaust energy can be used efficiently.

[Embodiment 3]
<Configuration of Third Embodiment> In the present embodiment, the exhaust jet control process shown in FIG. 5 is executed in the same cycle instead of the exhaust jet control process (FIG. 4) of the second embodiment. Except for the arrangement of the exhaust gas temperature sensor, which will be described later, the other configuration is the same as that of the second embodiment, and will be described with reference to FIG.
<Operation of Embodiment 3> The operation of the present embodiment will be described based on the processing of FIG. When this process is started, it is first determined whether or not there is a urea water injection request (S200). This process is the same as the process in step S100 of FIG. If there is no urea water injection request (NO in S200), a valve 122a closing command is output to the actuator 122b (S204). This process is the same as the process in step S104 of FIG. As a result, the high-temperature and high-pressure exhaust upstream of the turbine is not ejected from the ejection part 124 into the exhaust pipe 112 on the downstream side.

  If there is a urea water injection request (YES in S200), it is next determined whether the exhaust temperature is lower than the reference temperature (S201). Here, the exhaust temperature is the exhaust temperature in the exhaust pipe 112 on the downstream side of the turbine, and in this embodiment, the ECU 130 detects from the exhaust temperature sensor provided in the exhaust pipe 112 on the downstream side of the turbine. The reference temperature is such that the temperature of the exhaust gas flowing into the exhaust pipe 112 on the downstream side through the turbine is high, so that the urea water injected from the urea water addition valve 114 without the injection of high-temperature and high-pressure exhaust from the exhaust injection mechanism 126. Is set to a minimum exhaust temperature that is sufficiently agitated and hydrolyzed until it reaches the downstream SCR catalyst 120.

  If the actually measured exhaust temperature is not lower than the reference temperature (NO in S201), the high-temperature exhaust gas that has passed through the turbine vaporizes moisture of the urea water and causes severe expansion, and also rapidly hydrolyzes urea. Since it is possible, a closing command for the valve 122a is output to the actuator 122b (S204). As a result, even if high-temperature and high-pressure exhaust upstream of the turbine is not ejected from the ejection part 124 into the exhaust pipe 112 on the downstream side, the urea water is rapidly hydrolyzed and ammonia is uniformly dispersed to the downstream SCR catalyst 120. To reach.

On the other hand, if the actually measured exhaust temperature is lower than the reference temperature (YES in S201), the urea water does not expand rapidly due to the low-temperature exhaust gas that has passed through the turbine, and the urea may not be rapidly hydrolyzed. Then, an opening command for the valve 122a is output to the actuator 122b (S202). As a result, high-temperature and high-pressure exhaust upstream of the turbine is ejected from the ejection portion 124 into the exhaust pipe 112 on the downstream side. Accordingly, high-temperature and high-pressure exhaust gas flows from the ejection portion 124 at high speed into the space region Su in the exhaust pipe 112 into which urea water is injected from the urea water addition valve 114, and agitates while heating the sprayed urea water. . As a result, the temperature of the urea water is sufficiently raised to cause a rapid hydrolysis reaction, and ammonia can be supplied sufficiently uniformly to the downstream SCR catalyst 120.
<Effects of Third Embodiment> (1) The effects of the second embodiment are produced. At the same time, if the exhaust via the turbine is hot (NO in S201), the exhaust from the ejection part 124 is unnecessary, so the valve 122a is closed (S204), and the exhaust gas is unnecessarily high temperature and pressure. Is not ejected downstream of the turbine. For this reason, the use of exhaust energy becomes more efficient.

[Embodiment 4]
<Configuration of Embodiment 4> In the present embodiment, a jet portion 224 shown in FIGS. 6 and 7 is used in place of the jet portions 24 and 124 used in the first to third embodiments. The entire jet portion 224 has a ring shape, and is arranged over the entire circumference of the exhaust pipe 212 on the upstream side of the SCR catalyst 220.

An annular space 224 a is formed inside the ejection portion 224, and high-temperature and high-pressure exhaust on the upstream side of the turbine is supplied to the annular space 224 a via the bypass passage 222.
A jet outlet 224b for jetting high-temperature and high-pressure exhaust in the annular space 224a is formed inside the jet section 224. A plurality of, here four, jet nozzles 224b are arranged at equal phase intervals (here, 90 ° intervals). High-temperature and high-pressure exhaust gas in the annular space 224a is jetted from the jet port 224b into low-temperature and low-pressure exhaust gas flowing through the exhaust pipe 212 via the turbine.

The urea water addition valve 214 is attached to the exhaust pipe 212 so as to inject urea water from the upstream side of the ejection portion 224 to the central portion of the ejection portion 224 along the exhaust flow direction.
<Operation of Embodiment 4> When urea water injected from the urea water addition valve 214 passes through the central portion of the ejection portion 224 together with the exhaust flow, it is turned into high-temperature and high-pressure exhaust that is ejected from the ejection port 224b over the entire circumference. Be exposed.

For this reason, the urea water is vigorously stirred and heated to a high temperature, uniformly dispersed throughout the exhaust pipe 212, and rapidly hydrolyzed and flows into the SCR catalyst 220.
<Effects of Embodiment 4> (1) The effects of any of Embodiments 1 to 3 are produced. At the same time, when urea water flows in the center of the exhaust pipe 212, the space region Su is sufficiently stirred and heated by high-temperature and high-pressure exhaust jets from the surroundings, so that urea sticking to the inner wall of the exhaust pipe 212 is prevented. Can be complete.

[Other embodiments]
In each of the above embodiments, the bypass path for guiding the exhaust upstream of the turbine to the jet part on the downstream side of the turbine may be covered with a heat insulating material. As a result, the exhaust gas upstream of the turbine can be ejected without being cooled in the middle of the bypass, and the utilization efficiency of the exhaust energy is further increased.

  In the exhaust jet control process (FIGS. 4 and 5), when there is a urea water injection request, that is, high-temperature and high-pressure exhaust is jetted only during the urea water addition period, the urea water addition period and the exhaust jet period are May be set slightly longer than the urea water addition period, instead of synchronizing them completely. By doing in this way, the hydrolysis of urea in the urea water injected at the end of the urea water addition period can be ensured.

  In the exhaust gas ejection control process (FIG. 5) of the third embodiment, the presence / absence of exhaust gas ejection on the upstream side is determined based on the exhaust gas temperature downstream of the turbine (S201). As a result, the exhaust temperature and the exhaust flow state downstream of the turbine change, so the presence / absence of upstream exhaust injection may be determined based on the load of the diesel engine.

  2 ... diesel engine, 4 ... turbocharger, 4a ... compressor, 4b ... turbine, 6 ... intake pipe, 8 ... intercooler, 12 ... exhaust pipe, 14 ... urea water addition valve, 16 ... pump, 18 ... urea water storage tank, DESCRIPTION OF SYMBOLS 20 ... SCR catalyst, 22 ... Bypass path, 24 ... Injection part, 24a ... Accumulation chamber, 24b ... Inner side wall part, 24c ... Outlet, 26 ... Exhaust injection mechanism, 112 ... Exhaust pipe, 114 ... Urea water addition valve, 116 DESCRIPTION OF SYMBOLS ... Pump, 118 ... Urea water storage tank, 120 ... SCR catalyst, 122 ... Bypass path, 122a ... Valve, 122b ... Actuator, 124 ... Injection part, 126 ... Exhaust injection mechanism, 130 ... ECU, 212 ... Exhaust pipe, 214 ... Urea water addition valve, 220 ... SCR catalyst, 222 ... Bypass passage, 224 ... Jet section, 224a ... Annular space, 224b ... Jet port, Su ... Between the regions.

Claims (5)

Reduction in which an ammonia reducing agent is supplied to a catalyst arranged downstream of the exhaust pipe by injecting the ammonia reducing agent into the exhaust gas in the exhaust pipe from an addition valve arranged downstream of the turbocharger turbine in the exhaust pipe of the internal combustion engine An agent addition system,
A reducing agent addition system comprising: an exhaust jet mechanism for jetting exhaust gas upstream of the turbine in a space region in an exhaust pipe in an injection direction of the addition valve. 2. The reducing agent addition system according to claim 1, wherein the ammonia-based reducing agent is urea water. 3. The reducing agent addition system according to claim 1, wherein the exhaust injection mechanism includes a bypass pipe that bypasses the turbine from the upstream side to the downstream side, a valve provided in the bypass pipe, and a control unit that controls the valve. A reducing agent addition system characterized by comprising. 4. The reducing agent addition system according to claim 3, wherein the control unit controls the valve to eject exhaust gas upstream from the turbine in response to an addition period of the ammonia-based reducing agent from the addition valve. A reducing agent addition system characterized by that. 5. The reducing agent addition system according to claim 4, wherein when the exhaust temperature in a region where urea water is added as an ammonia-based reducing agent by the addition valve is lower than a reference temperature, the control unit includes the valve. And a reducing agent addition system characterized in that exhaust gas upstream of the turbine is ejected.